Image forming apparatus

ABSTRACT

If an edge of a sheet metal of a image forming apparatus damages an electric cable, the image signal is distorted and no correct image is formed since the damage causes feeding failure and signal deterioration. This is remarkable in the conventional digital electrophotographic apparatus, since the drive signal to drive a laser or a light emitting diode (LED) for exposing the photosensitive body becomes higher in frequency as a resolution and speed are increased and tends to generate the electric noise. In order to prevent damage of an electric cable by a metal frame, an apparatus having a holder for holding a feed cable is provided.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an image forming apparatus suchas a copying machine, facsimile apparatus and the like.

[0003] 2. Related Background Art

[0004] In general, an image forming apparatus of an electrophotographicsystem forms an electrostatic latent image by exposing a chargedphotosensitive body to an image light, and after this electrostaticlatent image is developed, it is transferred on a recording medium suchas a paper or the like.

[0005] In such an image forming apparatus, an electric cable is used forfeeding and transmitting a signal, which is usually fixed to a framemade of a sheet metal of the apparatus body.

[0006] As miniaturization of the apparatus has been progressing,restriction has come to be imposed on a wiring position and fixingposition of the cable and sometimes the cable may come into contact withan edge of the metal frame.

[0007] In this case, since the edge of the sheet metal frame is sharp,the electric cable may be damaged, thereby causing feeding failure andsignal deterioration.

[0008] Hence, a resin block is attached to the frame and the cable isfixed to this resin block, so that the cable can be prevented fromcontacting the edge.

[0009] However, since the resin block has an electric non-conductance,there arose a problem that an electric noise is generated when the cabletransmits a high frequency.

[0010] Particularly, in a digital electrophotographic apparatus, thedrive signal to drive a laser or a light emitting diode (LED) forexposing the photosensitive body becomes higher in frequency as aresolution and speed are increased and tends to generate the electricnoise.

[0011] When this noise is superposed on an image signal, the imagesignal is distorted and no correct image is formed.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide an image formingapparatus which prevents the damage of an electric cable by an metalframe.

[0013] Another object of the present invention is to provide the imageforming apparatus in which the electric cable can be installed.

[0014] Yet another object of the present invention is to provide theimage forming apparatus described in claims.

[0015] Yet further objects of the present invention will be apparentfrom the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a cross-sectional view of a schematic configuration ofan image forming apparatus according to an embodiment of the presentinvention;

[0017]FIG. 2 is a view showing a wiring of a feed cable provided for theimage forming apparatus;

[0018]FIG. 3 is a schematic view of a holder of the embodiment of thepresent invention;

[0019]FIGS. 4A, 4B and 4C are explanatory views explaining theconfiguration of the holder of the embodiment of the present invention;

[0020]FIG. 5 is an explanatory view explaining the wiring of theconventional feed cable;

[0021]FIGS. 6A and 6B are explanatory views explaining a method ofholding the feed cable; and

[0022]FIG. 7 is a prototype of an electric non-conductance resin holderbuilt by the present inventor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below withreference to the drawings.

[0024] First, an embodiment of the present invention will be described.

[0025] In the first place, an image forming process in the image formingapparatus adapting the electrophotographic system which is one exampleof the image forming apparatus according to the present embodiment willbe explained with reference to FIG. 1.

[0026] In such an image forming apparatus, as shown in FIG. 1, a first,a second, a third and a fourth image forming sections Pa, Pb, Pc and Pdwhich form images of respective colors of yellow, magenta, cyan andblack are installed. The image forming sections Pa, Pb, Pc and Pdcomprise photosensitive drums 17 a to d which are image bearing bodiesrespectively, and on which, after evenly charged by charging means 18 ato d, electrostatic latent images are formed by electrostatic latentimage forming means 19 a to d which use the light emitting diode as anexposure light source. After that, the electrostatic latent images aredeveloped by the toners of various colors by developing means 20 a to dand the toner images are electrostatically transferred on a recordingmedium by transfer means 21 a to d and then the toner images are fixedon the recording medium by heat and pressure of fixing means 12.

[0027] Under the above described first, second, third and fourth imageforming sections Pa, Pb, Pc and Pd from a cassette 11 which storesrecording papers as the recording medium to the fixing apparatus 12, arecording paper conveying belt as recording paper conveying means(hereinafter simply referred to as conveying belt) 13 in the shape of anendless belt which circularly moves through these image forming sectionsto convey the recording papers is installed.

[0028] The conveying belt 13 is a belt endlessly driven in the directionindicated by an arrow A by a drive roller 14 and bears the recordingpapers which are supplied from the cassette 11 and synchronized by apair of registration rollers 15 and fed and conveyed in order to theabove described image forming sections Pa, Pb, Pc and Pd.

[0029] The fixing apparatus 12 receives the recording paper dischargedfrom the drive roller 14 side and collectively fixes the toner images ofeach color, which are superposed and transferred on the recording paperin the image forming sections Pa, Pb, Pc and Pd, on the above describedrecording paper and forms a permanent image, and thereafter dischargesthe above described recording paper to a discharge tray 16.

[0030] A control line for electrically controlling the photosensitivedrums 17 a to d and the electrostatic latent image forming means 19 a tod and the like of the above described image forming sections Pa, Pb, Pcand Pd and a feed cable 24 which is a power source line for supplying anelectric power to the image forming sections Pa, Pb, Pc and Pd finallyreach, as shown in FIG. 2, the power source (not shown) and a controlsubstrate 22 through the metal frame. These power source and controlsubstrate 22 are usually installed at the rear of the apparatus. In thevicinity of the image forming sections, driving sources 23 a and 23 bare installed respectively. In the case where these driving sources 23 aand 23 b avoid the metal frame 21 and try to secure a passage for thefeed cable 24, a wiring passage inevitably becomes long. Particularly inthe case of the present embodiment such as the image forming apparatuscomprising four image forming sections, the installation of the feedcable 24 is complicated. In order to make the wiring passage of the feedcable 24 the shortest, it is desirable to take out the feed cable 24from the position close to the rear of the metal frame 21 in the imageforming sections.

[0031] However, if the feed cable 24 is attached to the metal frame 21as it is, the edge of the metal frame 21 inflicts damage to the feedcable 24.

[0032] Therefore, the present inventor attached a holder 205 (FIG. 7)made of electric non-conductance resin to the metal frame 201, whichprotects and holds the feed cable 204. Nevertheless, since the feedcable 204 has been transmitting high frequency electric signals,electric noises were produced, which were superposed on the highfrequency electric signals, thereby disturbing the images.

[0033] In view of the above, the present patent inventor has attached,as shown in FIG. 3, a holder 30 comprising a substrate 25 made of resinand an electro-conductive sheet 28 to a metal frame 21.

[0034] The electro-conductive sheet 28, as shown in FIG. 3 and FIG. 4A,is installed in such a manner as to go around from the holding surfaceside of the feed cable 24 of the holder 30 to the metal frame 21contacting surface side of the holder 30 through the feed cable pressingmember 29, so that the feed cable 24 held by the holder 30 can beelectrically connected to the metal frame 21.

[0035] When constituted in such a manner, the feed cable 24 is notbrought into contact with the metal frame 21 and therefore is notdamaged by the edge of the metal frame 21. Further, since the feed cable24 is grounded to the metal frame 21 through the electro-conductivesheet 28, the electric noises are removed and have no influence on theimages. Furthermore, being made of resin, the substrate can be obtainedin a desired shape and is inexpensive comparing to a metal made.

[0036] Here, a method of holding the feed cable 24 in the image formingapparatus according to the present embodiment will be described.

[0037] Between a gap d2 of the feed cable pressing member 29 of theholder 30 and a line diameter d1 of the feed cable 24, there exists arelationship of d2<d1 as shown in FIG. 4B and therefore, in a state inwhich the feed cable 24 is fitted with the pressing member 29, the feedcable 24 is pressed against the electro-conductive sheet 28. As aresult, an earth can be securely taken between the feed cable 24 and themetal frame 21 through the electro-conductive sheet 28.

[0038] The electro-conductive sheet 28 is, as shown in FIG. 4C, dividedinto plural layers.

[0039] As an example of the layers constituting the electro-conductivesheet 28, a first combination can be enumerated as follows:

[0040] A first layer . . . a surface electro-conductive layer,

[0041] A second layer . . . an adhesive layer.

[0042] Or a second combination as follows:

[0043] A first layer . . . a surface electro-conductive layer,

[0044] A second layer . . . a resin layer.

[0045] Or a third combination as follows:

[0046] A first layer . . . a surface electro-conductive layer,

[0047] A second layer . . . a resin layer,

[0048] A third layer . . . an adhesive layer.

[0049] Having the adhesive layer is much easier in attaching theelectro-conductive sheet 28 to the substrate 25 of the holder 30 andexcellent in working performance. Having the resin layer reinforces theelectro-conductive layer 28 and makes it easy to handle. Note that theelectro-conductive sheet 28 made of any combination of the abovedescribed layers can be realized at relatively low cost. Further, incase of abolishing the image forming apparatus, removal of the sheetportion only of the holder 30 allows the remaining resin substrate 25 tobe utilized once again. At this time, if the electro-conductive sheet 28is installed in the resin substrate 25 in such a manner as to be easilypeeled off, it can be more easily utilized.

[0050] Incidentally, in the present embodiment, for the sake ofsimplicity, a location of the holder 30 is limited, but the location isessentially not to be limited. Further, in the present embodiment,though the image forming apparatus comprising four image formingsections was employed, it is not limited to this configuration. Further,in the present embodiment, though lead wires of the image forming meansare connected to the power source or the substrate, the connecting pointis not limited to this.

[0051] The foregoing embodiments are included merely to aid in theunderstanding of the invention. However, it is to be understood that theinvention is not intended to be limited to the embodiments, andvariations may be made by skilled in the art without departing from thespirit and the scope of the invention.

What is claimed is:
 1. An image forming apparatus comprising: an imagebearing body; image forming means for forming an image on the imagebearing body; a feed cable for transmitting an electrical signal to theimage forming means; a holder for holding the feed cable, the holderhaving a substrate made of resin and an electro-conductive sheetinstalled on the substrate; and a metal frame attached to the holder;wherein the electro-conductive sheet is installed in such a manner as tocontact the feed cable and the metal frame.
 2. An image formingapparatus according to claim 1, wherein the electro-conductive sheet isremovably adhered on the substrate.
 3. An image forming apparatusaccording to claim 1, wherein the electro-conductive sheet comprises aresin layer and a surface electro-conductive layer.
 4. An image formingapparatus according to claim 1, wherein the image forming means comprisean LED which emits a light beam in response to an image forming signal,and the feed cable transmits image signals to the LED.
 5. An imageforming apparatus according to claim 1, wherein the feed cable transmitshigh frequency electric signals, and the feed cable is grounded to themetal frame by the electro-conductive sheet, thereby reducing highfrequency noises.
 6. An image forming apparatus according to claim 1,wherein the image forming apparatus further comprises a fixing memberwhich pressingly fixes the cable to the electro-conductive sheet.
 7. Animage forming apparatus according to claim 6, wherein the image formingapparatus comprises a fixing member which inserts the feed cable from afirst direction and a plurality of fixing members which fix the feedcables from a second direction.